An éclair is a delicate, individual pastry made with choux pastry (choux paste, pâte à choux, cream puff pastry dough). The dough is piped from a pastry bag in an oblong or log shape onto baking pans, and baked until it is crisp and hollow inside. It is either filled from a hole made in one end, or split lengthwise and filled. The filling is traditionally a vanilla pastry cream (crème pâtissière), or whipped cream, and usually topped with a chocolate fondant or confectioners’ glaze.
The Oxford English Dictionary traces the term "éclair" in the English language to 1861. The first known recipe for éclairs appears in the Boston Cooking School Cook Book by Mrs. D.A. Lincoln, published in 1884.
"Éclair" is the French word for lightning. It is believed that the pastry received its name because it glistens when coated with confectioner's glaze!